A large-scale, high speed, high resolution, phase-only microelectromechanical system (MEMS) spatial light modulator (SLM) has been fabricated. Using polysilicon thin film technology, the micro mirror array offers significant improvement in SLM speed in comparison to alternative modulator technologies. Pixel opto-electromechanical characterization has been quantified experimentally on large scale arrays of micro mirrors and results are reported.
The National Science Foundation Center for Adaptive Optics (CfAO) is coordinating a program for the development of spatial light modulators suitable for adaptive optics applications based on micro-optoelectromechanical systems (MOEMS) technology. This collaborative program is being conducted by researchers at several partner institutions including the Berkeley Sensor & Actuator Center, Boston Micromachines, Boston University, Lucent Technologies, the Jet Propulsion Laboratory, and Lawrence Livermore National Laboratory. The goal of this program is to produce MEMS spatial light modulators with several thousand actuators that can be used for high-resolution wavefront control applications that would benefit from low device cost, small system size, and low power requirements. The two primary applications targeted by the CfAO are astronomy and vision science. In this paper, we present an overview of the CfAO MEMS development plan along with details of the current program status.
This paper presents a high-speed resolution phase-only microelectromechanical system (MEMS) spatial light modulator (SLM), integrated with driver electronics, using through- wafer vias and solder bump bonding. It employs a polysilicon thin film MEMS technology that is well suited to micromirror array fabrication and offers significant improvement in SLM speed in comparison to alternative modulator technologies. Vertical through-wafer interconnections offer scalability required to achieve 1M-pixel array size. The design, development, fabrication and characterization of a scalable driver integrated SLM is discussed. Pixel opto- electromechanical performance has been quantified experimentally on prototypes, and results are reported.
Researchers at Lawrence Livermore National Laboratory are developing means to collect and identify fluid-based biological pathogens in the forms of proteins, viruses, and bacteria. To support detection instruments, we are developing a flexible fluidic sample preparation unit. The overall goal of this Microfluidic Module is to input a fluid sample, containing background particulates and potentially target compounds, and deliver a processed sample for detection. We are developing techniques for sample purification, mixing, and filtration that would be useful to many applications including immunologic and nucleic acid assays. Many of these fluidic functions are accomplished with acoustic radiation pressure or dielectrophoresis. We are integrating these technologies into packaged systems with pumps and valves to control fluid flow through the fluidic circuit.
The NSF Center for Adaptive Optics (CfAO) is coordinating a five to ten year program for the development of MEMS-based spatial light modulators suitable for adaptive optics applications. Participants in this multi-disciplinary program include several partner institutions and research collaborators. The goal of this program is to produce MEMS spatial light modulators with several thousand actuators that can be used for high-resolution wavefront control applications and would benefit from low device cost, small system size, and low power requirements. We present an overview of the CfAO MEMS development plan along with details of the current program status. Piston mirror array devices that satisfy minimum application requirements have been developed, and work is continuing to enhance the piston devices, add tip-tilt functionality, extend actuator stroke, create a large array addressing platform, and develop new coating processes.
A slide-together compression package and microfluidic interconnects for microfabricated devices requiring fluidic and electrical connections is presented. The package assembles without tools, is reusable, and requires no epoxy, wirebonds, or solder, making chip replacement fast and easy. The microfluidic interconnects use standard HPLC PEEK tubing, with the tip machined to accept either an o-ring or custom molded ring which serves the dual function of forming the seal and providing mechanical retention strength. One design uses a screw to compress the o-ring, while others are simply plugged into a cartridge retained in the package. The connectors are helium leak-tight, can withstand hundreds of psi, are easy to connect and disconnect, are low dead volume, have a small footprint, and are adaptable to a broad range of microfabricated devices.
The electrostatic comb finger drive has become an integral design for microsensor and microactuator applications. This paper reports on utilizing the levitation effect of comb fingers to design vertical-to-the-substrate actuation for interferometric applications. For typical polysilicon comb drives with 2 micrometers gaps between the stationary and moving fingers, as well as between the microstructures and the substrate, the equilibrium position is nominally 1-2 micrometers above the stationary comb fingers. This distance is ideal for many phase shifting interferometric applications. Theoretical calculations of the vertical actuation characteristics are compared with the experimental result, and a general design guideline is derived from these result. The suspension flexure stiffness, gravity forces, squeeze film damping, and comb finger thicknesses are parameters investigated which affect the displacement curve of the vertical microactuator. By designing a parallel plate capacitor between the suspended mass and the substrate, in situ position sensing can be used to control the vertical movement, providing a total feedback-controlled system. Fundamentals of various capacitive position sensing techniques are discussed. Experimental verification is carried out by a Zygo distance measurement interferometer.
Contamination particles of controlled size and shape were deposited onto 1.14 cm thick fused silica windows by sputtering Al through a mask. The particles were 1 micrometers thick circular dots, 10 to 250 micrometers in diameter. Al shavings were also deposited on the windows to investigate the effects of particle-substrate adhesion. The silica windows were then illuminated repetitively using a 3-ns, 355 nm and an 8.6-ns, 1064 nm laser. The tests were conducted at near normal incidence with particles on the input and output surfaces of the window. During the first shot, a plasma ignited at the metal particle and damage initiated on the fused silica surface. The morphological features of the damage initiated at the metal dots were very reproducible but different for input and output surface contamination. FOr input surface contamination, minor damage occurred where the particle was located; such damage ceased to grow with the removal of contaminant material. More serious damage was initiated on the output surface and grew to catastrophic proportions after few shots. Output surface contaminants were usually ejected on the initial shot, leaving a wave pattern on the surface. No further damage occurred with subsequent shots unless a shot cracked the surface; such behavior was mostly observed at 355 nm and occasionally for large shavings at 1064 nm. The size of the damaged area scaled with the size of the particle. The onset of catastrophic damage on the output surface occurred only when particles exceeded a critical size. The damage behavior of the sputtered dots was found to be qualitatively similar to that of the shavings. The artificial contamination technique accelerated the study by allowing better control of the test conditions.